Security systems are widely used to protect property and provide personal safety. Security systems generally include a control unit that controls the overall operation of the system, one or more keypads providing user access to the system, and various detectors and sensors.
Security systems may generate an alarm in response to any number of events, such unauthorized entry, fire, medical emergency or manual alarm activation. The security system may be associated with a service that remotely monitors the status of the security system. Thus, if the security system generates an alarm, a notification signal may be transmitted via a wired and/or wireless communications link to a monitoring system. Upon receiving the notification, security service personnel for the monitoring system may attempt to contact the property owner or other party at the facility to verify the alarm. If it is appropriate to do so, a security service representative may, upon confirmation of the alarm, contact an emergency response agency such as the police department, the fire department, an emergency medical team, or other appropriate entity. Security systems are also playing a larger role in building automation, and may include a control unit that provides building automation features.
The control unit often communicates wirelessly with one or more of the devices in the system. As a result, the control unit requires antennas to allow radio frequency (RF) communications. A single control unit may require antennas for Z-Wave communications, Wi-Fi communications, Global System for Mobile Communications (GSM) communications, or others.
Designing antennas to fit within the enclosure of the control unit poses challenges. The control unit, with its various electronic components, is a “noisy” environment and antennas need to be protected from electromagnetic interference (EMI). The antennas must also be small enough to fit within the casing for the control unit. An antenna designer may have to compromise other characteristics of the antenna (such as efficiency, bandwidth, and gain) to create an antenna with the necessary dimensions. At the same time, there are benefits to keeping the antennas within the control unit; for example, the control unit casing protects the antennas from physical damage and from the elements. An external antenna can also be unsightly. In some situations, it would be desirable to have an antenna for a control unit that can be external to the control unit, but without the dangers of exposure.